Iranians are voting Friday to elect a new president amid tight security and in an electoral process highly controlled by the regime.

Citizens can choose one of six remaining candidates who were approved by a panel of Iran's ruling clerics. Most are considered hardliners who support the government structure and are loyal to the country's supreme leader.

Iran sealed most of its borders, rounded up dissidents and detained some journalists. Most foreign news organizations say their attempts to get visas to cover the election were unheeded by the government.

Some 55 million Iranians are eligible to vote.

Iranians will choose the successor to two-term President Mahmoud Ahmadinejad, who is constitutionally barred from a third consecutive term

Iran's supreme leader, Ayatollah Ali Khamenei, has been calling for Iranians to show up to vote in large numbers.

In a speech this week that was reported by the state-run ISNA news agency, Ayatollah Khamenei said "the strong presence of the Iranian nation will disappoint the enemy, make it reduce pressures and follow another path."

Heading into the campaign, many analysts viewed Iran's chief nuclear negotiator, Saeed Jalili, as the likely favorite. But moderate candidate and former nuclear negotiator Hassan Rowhani has been gaining prominence in recent days.

One candidate seen as reformist, Mohammad Reza Aref, dropped out this week and then announced his support for Rowhani. Another candidate, Gholam Ali Haddad Adel, dropped out of contention Monday saying he wanted to boost the chances of his fellow conservatives.

The election winner will be faced with an economy struggling with high unemployment and inflation, crippled by international sanctions imposed over Iran's disputed nuclear program.

While some candidates have voiced support for improved ties with the international community, major policy decisions rest with the supreme leader.

To win, a candidate must get 50 percent of the vote. If no one succeeds after the initial vote, a runoff election will be scheduled a week later.